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small fragnients of fine-grained diorite. But it also encloses 

 on the south and west shores much larger masses of what 

 appears at first sight to l)e the older and more basic granite of 

 medium texture. The contacts are, however, somewhat ambigu- 

 ous, a[>poaring to favor the view that the finer-grained granite 

 is the newer, and hence to be correlated with the third or 

 microgranitic type. By fixr the greater part of the granite 

 evidently belongs to the newer variety, the typical, sparingly 

 hornblendic, usually coarsely and distinctly crystalline, gray to 

 pink or red granite of the South Shore district. This is 

 especially true where the granite is not most intimately associated 

 with the diorite. The hornblendic element, as in Cohasset, is 

 very generally replaced partially, sometimes wholly, by mica 

 (chiefly biotite). This is seen very clearly in the abandoned 

 quarry on Long Bridge Lane, which is, with one exception, the 

 only point in flingham where the granite, or any rock, has 

 been systematically quarried. The fclds})ar (orthoclase) is 

 commonly gray or pink, more rarely green, at least in part; 

 and, very locally, as in some of the ledges along Thaxter 

 Street, it is porphyritically developed. 



Undoubtedly, one of the most interesting exposures of 

 granite in Hingham is the small quarry about one third of a 

 mile northeast of Abington Street, in the southwest corner of 

 the town, and nearly two miles beyond the limits of the map. 

 On going in from Abington Street by the quarry road, the 

 ordinary, coarse, biotite granite gives w^ay, with apparent 

 abruptness, to a finely crystalline, homogeneous, light gray 

 variety, which is rich in quartz, and contains but little of any 

 dark accessory. The other limits of the fine granite were not 

 observed, but it appears to cover a considerable area. The 

 feature of j)articular interest which it presents is the remarkably 

 perfect parallel joint-structure. In fact, it is the jointing that 

 o-ives the granite its value as a quarry-stone. The parallel 

 jointing is traceable over an area at least 500 feet long north 

 and south, and half as broad ; but it is most perfectly devel- 



